I've been using https://httpbin.org/ to so some client testing and so far it has been great. They provide a docker image which makes it easy to run locally.

> One thing I like doing when working with APIa is to have an echo server at hand.

> I.e. something that I can query via curl or via a network library that I’m using, and see in response what kind of request it actually received. It helps me verify that I’m making correct requests (and not misusing curl or a network library).

Did you consider using a proxy during development. A man-in-the-middle server that does nothing but relay and record all communications between client and server?

I made one specifically for this use-case. See it in action (3m video): https://www.youtube.com/watch?v=kpsFSY-G5F0

I use ZAP [1] with the OAST add-on for this at the moment. I admit the UX isn't perfect, but it serves my purpose.

If I also want control over the responses (e.g. return a 401 status code for every fifth request), I have a custom extender script [2] for that.

[1]: https://www.zaproxy.org/

[2]: https://www.zaproxy.org/blog/2022-09-13-zap-extender-scripts...

    <?php
    print_r($_POST);
    print_r($_GET);

If all you need is an echo, should be as simple as this in a .php file, no? Can be deployed with PHP's built-in webserver.

Sounds like mockserver[0] might be what you want.

[0] https://www.mock-server.com/

Sound like you need https://mitmproxy.org/#mitmweb